Don't Feed Your Resume to a Cover Letter Prompt

The most common way people generate a cover letter is to paste their resume, paste the posting, and ask for a letter. It works, in the sense that a letter comes out. What comes out is your resume converted into prose — the same facts, in paragraphs, with connectives. The reader already has your resume attached to the same email, so you have spent their attention restating what they can see, and the one thing a letter can do that a resume cannot has not happened.

Why the resume is the wrong input

Give a model one document and ask it for a different document, and the operation it performs is conversion. It has no other material. Your resume is a list of compressed claims; a letter is prose; so it decompresses the claims into sentences and adds transitions. That is a faithful execution of the request.

You can see it in the output. The letter’s second paragraph walks your most recent role and names the same two achievements the resume bullets name. The third paragraph does the same for the role before. The verbs are slightly warmer. Nothing is untrue and nothing is new.

The specific loss is that a resume has already had the reasoning removed from it. Bullets state outcomes; they do not state why you made the choices you made, what was hard, or what you learned that someone outside the work would not guess. A model reading only your bullets cannot recover any of that, because it was never written down. So it fills the space with the material it does have — adjectives about the employer and enthusiasm about the opportunity.

What to give it instead

Supply the things that were deliberately left off the resume:

One piece of work, described at length and badly. Not the bullet — the account. What the situation actually was, what you tried, what did not work, what you would do differently. Three hundred rough words about one project is more useful than a complete resume, because it contains the reasoning the resume compressed out.

What was surprising about it. The thing people who have not done this job assume wrongly. A model cannot generate this and cannot fake it, which is exactly why it is worth supplying.

Why you are writing to this employer specifically — the real reason, even if it is unglamorous. The work is close to something you want to do more of; the team is small enough that the job would be broad. A real reason plainly stated beats admiration for their commitment to innovation, which is the sentence you get when you supply no reason at all.

A negative list. What is not true and must not appear. I have not used their product. I have three years, not five. Do not claim familiarity with this sector. Use no numbers except the two I gave you. Without this, the model closes gaps, and closed gaps are where invented specifics live.

Then ask for something narrower than a letter. Organise the notes above into three paragraphs, using only facts I supplied gets you further than write a cover letter, because the second request invites the genre and the genre is the problem.

The overlap audit

This is the check that is specific to having a resume in play, and it takes two minutes.

Put the resume and the draft letter side by side. Go through the letter sentence by sentence and mark every sentence whose factual content already appears on the resume. Then look at how much of the letter is marked.

If most of it is, the letter is a duplicate and the fix is subtraction, not rewriting. Cut the marked sentences. What remains is either the letter’s actual content or nothing — and finding out which is the useful outcome. If nothing remains, you have not yet supplied the material a letter needs, and no prompt will conjure it.

Some overlap is fine and necessary; a letter that never touches your experience is not a letter. The signal you are looking for is a letter that is entirely overlap.

The two claims to check hardest

Claims about you that the resume does not support. A letter has more room than a resume, and room is where scope grows. A bullet saying you handled the supplier schedule becomes a paragraph about managing supplier relationships. That is the same drift documented for resume bullets in where AI-drafted bullets drift from the truth, and it is worse in a letter because prose hides it better — there is no parallel structure to make the change visible.

The check is the same one you apply to bullets: does each claim trace to something in your own record? A letter deserves the pass as much as the resume, and rarely gets it.

Claims about the employer. These are new, because your resume contains none. A model asked to write about a company will produce statements about it, and you have no basis for any of them. It may describe a market position, a product, or a direction that is out of date or simply generated. You will not catch these by reading for tone, because they are not tone — they are assertions of fact about a third party, and you are the one signing the letter.

Rule: no sentence about the employer that you did not verify yourself and could not source if asked. If you have not looked into them enough to write one true sentence about them, that is worth knowing before you apply.

Consistency with what else you are sending

The letter goes in the same file as the resume and the form answers. If the letter says you led something the resume says you supported, the discrepancy is visible to the one person you did not want to notice it. Draft both from the same short block of settled facts rather than from each other — the mechanics are in using AI across a whole application, and the reason the phrasing matters is the verb you choose is a claim.

The order

1. Pick the one piece of work the letter will be about. Yours to choose.
2. Write the long, ugly account of it, plus what surprised you, plus your real reason for writing.
3. Session: organise that material into paragraphs, with the negative list attached. Do not paste the resume.
4. Run the overlap audit against the resume. Cut duplicates.
5. Check every claim about you against your record, and every claim about the employer against something you actually read.
6. Rewrite the first and last sentences in your own words.
7. Read it aloud and change anything you would not say.

Step 3’s instruction not to paste the resume is the one that changes the output. Everything else is hygiene you would apply anyway. If you also want to know how a general-purpose model handles the resume side of the same application, that is driving an AI session on your resume; the narrower question of what a model can and cannot know about the company you are writing to is what AI does not know about the employer.